Adaptive lighting system for even illumination

ABSTRACT

An adaptive lighting system for even illumination is provided. In an embodiment, multiple lamps illuminate light in different areas or zones of the surroundings. These lamps modulate their light output in a known (but imperceptible) pattern. One or more light detectors detects light from the surroundings. Light sourced from each lamp is disambiguated and one or more light time-of-flight delays are calculated for each lamp-light detector pair. Based on these calculated delays, illumination levels of the lights are adjusted so as to produce even illumination.

The present application is a continuation of patent application Ser. No.17/273,085 entitled “ADAPTIVE LIGHTING SYSTEM FOR EVEN ILLUMINATION”filed on Mar. 3, 2021 at the USPTO, which in turn claimed the benefit ofand priority from provisional patent application 201821033146 titled“ADAPTIVE LIGHTING SYSTEM FOR EVEN ILLUMINATION” filed in Mumbai, Indiaon 4 Sep. 2018.

FIELD

This patent relates to illumination. More specifically, the patentrelates to an adaptive lighting system for even illumination.

BACKGROUND

Miners, rescue workers, security personnel, certain constructionworkers, astronauts, divers wear helmets or suits that have inbuiltlamps to illuminate their surroundings. The lamps have to be powerfulenough to illuminate dark surroundings, but as a result, as thesepersonnel walk close to certain objects, walls, obstructions etc., thelight falling on these objects is so bright as to cause visualdiscomfort to the personnel. Visual discomfort aside, there is morelight falling on nearby objects and less light falling on distantobjects thus giving uneven illumination and hampering visibility.

The present invention is a wearable/portable system for evenillumination; which can be used by such personnel to achieve evenillumination in dark surroundings.

SUMMARY

An adaptive lighting system for even illumination is provided. In anembodiment, multiple lamps illuminate light in different areas or zonesof the surroundings. These lamps modulate their light output in a known(but imperceptible) pattern. One or more light detectors detects lightfrom the surroundings. Light sourced from each lamp is disambiguated andone or more light time-of-flight delays are calculated for eachlamp-light detector pair. Based on these calculated delays, illuminationlevels of the lights are adjusted so as to produce even illumination.

The above and other preferred features, including various details ofimplementation and combination of elements are more particularlydescribed with reference to the accompanying drawings and pointed out inthe claims. It will be understood that the particular methods andsystems described herein are shown by way of illustration only and notas limitations. As will be understood by those skilled in the art, theprinciples and features described herein may be employed in various andnumerous embodiments without departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included as part of the presentspecification, illustrate the presently preferred embodiment andtogether with the general description given above and the detaileddescription of the preferred embodiment given below serve to explain andteach the principles of the present invention.

FIG. 1 depicts a system of producing even illumination provided on ahelmet.

FIG. 2 depicts a system in which a single detector receives reflectedlight that started at more than one lamps.

FIG. 3 depicts a system to disambiguate reflections from one or morethan one lamps.

FIG. 4 depicts a cross correlator as a schematic circuit.

FIG. 5 depicts another cross correlator as a schematic circuit.

FIG. 6 depicts a typical cross correlation sequence from a crosscorrelator.

FIG. 7 depicts another typical cross correlation sequence from a crosscorrelator.

FIG. 8 depicts yet another typical cross correlation sequence from across correlator.

FIG. 9 depicts a situation wherein a system of producing evenillumination provided on a helmet is illuminating a room.

FIG. 10 depicts an on-off flashing sequence.

FIG. 11 depicts a sinusoidal flashing sequence.

FIG. 12 depicts a sinusoidal flashing sequence with modulation depthless than 100%.

FIG. 13 depicts a square wave flashing sequence with modulation depthless than 100%.

FIG. 14 depicts a random on-off flashing sequence.

FIG. 15 depicts a random square wave flashing sequence with modulationdepth less than 100%.

FIG. 16 depicts a flashing sequence with more than two levels andmodulation depth less than 100%.

FIG. 17 depicts a law of calculating the illumination of a lamp based onthe detected distance.

FIG. 18 depicts another law of calculating the illumination of a lampbased on the detected distance.

FIG. 19 depicts yet another law of calculating the illumination of alamp based on the detected distance.

FIG. 20 depicts a system of producing even illumination provided on ahand-held rod.

FIG. 21 depicts a system of producing even illumination provided on ahand-held illuminator.

FIG. 22 depicts a system of producing even illumination provided on avehicle.

FIG. 23 depicts a system of producing even illumination provided on arig.

DETAILED DESCRIPTION

An adaptive lighting system for even illumination is provided. In anembodiment, multiple lamps illuminate light in different areas or zonesof the surroundings. These lamps modulate their light output in a known(but imperceptible) pattern. One or more light detectors detects lightfrom the surroundings. Light sourced from each lamp is disambiguated andone or more light time-of-flight delays are calculated for eachlamp-light detector pair. Based on these calculated delays, illuminationlevels of the lights are adjusted so as to produce even illumination.

FIG. 1 depicts a system 100 of producing even illumination provided on ahelmet 101.

One or multiple lamps 102 are provided on a helmet 101. Alternatively,the multiple lamps 102 may be mounted on any single body such as ahand-held rod, on a vehicle, on a rig, etc. Each lamp 102 illuminates anarea or zone of the surroundings. Each lamp 102 produces flashes oflight at a very high speed. The speed of flashing is chosen to be muchfaster than the human eye can detect, so that the human eye seesconstant illumination. The speed of flashing may also be chosen to bemultiple times the speed of movie or video camera shutters or framerates, so that video/movie cameras do not capture any flashing either.The flashing may not be of an on-off type but some other kind ofmodulation, with some modulation depth. For example sinusoidal or squarewave modulation of a depth equal to or less than 100% may be used.

One or more light detectors 103 are placed on the same body 101 as thelamps. The body 101 on which the lamps 102 and detectors 103 are placedmay be a rigid body in parts where the lamps 102 and detectors 103 aremounted, such that the geometric relations of the lamps 102 anddetectors 103 with respect to each other remain fixed. Light from thelamps 102 travels to various surrounding objects 110, reflects back fromthem and enters the one or more light detectors 103. This light getsdelayed by an amount equivalent to the sum of the two travel times. Thisdelay is detected, and from this detection, the distance to the object110 illuminated by each lamp 102 is detected. The total illuminationoutput of each lamp 102 is then adjusted in such a way that uniformillumination on all illuminated objects is achieved. In general, lampsilluminating closer objects will produce less illumination output thanlamps illuminating farther objects. For example, illumination may beincreased directly proportional to the square of the detected distance.Beyond a certain large distance, a different law may be used, and fordistances smaller than a certain small distance, a different law may beused as well. The total illumination may not be adjusted immediatelywhen a change in light delays is observed, but at a slightly slower(smoothened) pace so that jarring flashes of light are not observed bythe user. In the case an accelerometer is also provided as part of theapparatus, changes in orientation can be detected quickly and lightingchanges to compensate for changes in orientation can be done very fast,but lighting changes due to other detected changes can still be sloweddown or their transitions can be smoothened.

The system 100 is especially helpful in situations where the system 100is illuminating surroundings which will otherwise be completely ormostly dark. Such a situation may occur in mining, forest operations,maintenance situations, emergency rescue operations, securityoperations, submarine or space operations, etc. By ensuring evenillumination on all illuminated objects, the visibility of thesurroundings is enhanced, comfort is increased, and power is spentoptimally.

FIG. 2 depicts a system 200 in which a single detector 203 receivesreflected light that started at more than one lamps 202. The lamps 202are illuminating various objects 210 and the distance to these variousobjects 210 from the system 200 may not be the same. Light reflected bythe various objects 210 is detected by the detector 203. In this case,an algorithm is used to disambiguate the reflections from each of thelamps using the flashing sequence.

FIG. 3 depicts a system 300 to disambiguate reflections from one or morethan one lamps 302.

Each lamp 302 has a separate flashing sequence 304, and the flashingsequences 304 are chosen such that various flashing sequences 304 areuncorrelated with each other, even after various shifts. For examplesuch flashing sequences may be periodic waveforms (sinusoidal, squarewave or other waveforms) of different frequencies, or random orpseudo-random sequences of bits or numbers.

The signal detected at the detector 303 is a mix of the one or more thanone flashing sequences 304 with various delays. Using one or more crosscorrelators 305 the contribution of individual flashing sequences 304 isdisambiguated in the signal detected at the detector 303, and delays aredetected as well. The cross correlators 305 may be embedded in thedetector 303 itself, or they may be analog electronic circuits, ordigital electronic circuits, or software.

In case there are more than one light detectors, similar disambiguationstructure may be repeated for every detector.

FIG. 4 depicts a cross correlator 405 as a schematic circuit.

In an embodiment, the cross correlator 405, corresponding to aparticular lamp and detector pair, and produces a cross correlationsequence at each time step. The cross correlation at a time step j for asignal delay of k may be calculated as

c _(j)(k)=(1/a)c _(j−1)(k)+d(j)f(j−k)

-   -   where c_(j) is the cross correlation calculated at the j^(th)        time step, c_(j−1) is the cross correlation calculated at the        j−1^(th) time step, d is the detected signal at the light        detector and f is the flashing sequence used by the lamp.

FIG. 5 depicts another cross correlator 505 as a schematic circuit. Aflashing sequence 504 is a periodic sequence, such as a square wave orsinusoidal sequence. This sequence is phase shifted by 90 degrees byphase shifter 506. (Alternatively, both the flashing sequence 504 andits phase shifted version 507 are created together by an oscillator,circuit or computation.) Both the original sequence 504 and its phaseshifted version sequence 507 are mixed in mixers 508 and 509 with thedetected signal. The mixing is a nonlinear combination of the twosignals such as a multiplication of the two signals, or adding the twosignals and then passing them through a non-linear amplifier (such as anon-linear function or a crystal (diode/transistor) based amplifier,etc.). The mixer also has a means for filtering out of higher frequencycomponents and keeping low frequency components. The nonlinearcombination and filtering may be done using an analog electronic circuitor other analog component (such as a SAW filter), or a digital circuitor a computation. The nonlinear combination may also be done directly atthe optical detector by modifying the sensitivity of the opticaldetector using the flashing sequence (original or phase shifted). Thismay be done for example by applying and removing the electronic shutterpotential of a CCD or CMOS sensor, changing the amplification factor ofa light signal detection circuit (or amplifier), by changing the opacityof an LCD or other optical shutter, or changing the aperture of amechanical shutter.

The two values detected by the two signals can be converted into a phaseangle (taking the arc tangent of the ratio of the two values, or theatan 2 of the two values), and this phase angle can be used detect thetime delay taken by the light in traveling from the lamp to thedetector. In an embodiment, various light components of a lamp (forexample red/green/blue light components or yellow/blue light components)are flashing at different flashing frequencies. The light detectorcomprises filters that separate the light components and each lightcomponent is separately detected by a light detector. In this way, phaseangles at multiple flashing frequencies may be detected, and the totaldelay between the lamp and the detector can be calculated better thisway. In particular, the total delay d (to be detected) follows thefollowing equations (one for each light component)

d=k ₁ t ₁ +p ₁

d−k ₂ t ₂ +p ₂

-   -   where k_(i) are unknown integers, t_(i) are the flashing time        periods and p_(i) are the detected phase angles. Since d and        k_(i) are unknown, a single equation cannot be solved, but        multiple such equations can be solved if the range of d is known        to be a finite range. If two three or more such phase angles        p_(i) are available at different flashing frequencies (and thus        different t_(i)) d is chosen such that there exist integers        k_(i) such that the sum of errors in the above equations is a        minimum.

The more than one lamps of the system of the present invention will beflashing at different frequencies; thus the effect of the light of onelamp on the correlator output correlating with the signal of anotherlamp will be minimal.

FIG. 6 depicts a typical cross correlation sequence 604 from a crosscorrelator.

This cross correlation sequence is a sequence of numbers labeled bydelays; a number in the sequence is labeled by a particular delay valuethat corresponds to a specific time delay of light traveling from theparticular lamp to the particular detector.

FIG. 7 depicts another typical cross correlation sequence 704 from across correlator.

A peak 711 at a particular delay value 712 indicates that the indicateddelay has been observed in the cross correlation. The peak is detectedby a peak detection algorithm. The delay value corresponding to thedetected peak is converted to a distance by multiplying by the speed oflight, and optionally dividing by two to convert from round-tripdistance to single distance. The distance is then converted to a lampillumination parameter. Instead of converting the delay to a distance,the delay may be converted directly to the lamp illumination parameter.The lamp illumination parameter may be in terms of optical lamp outputor lamp power output, or it may be in terms of a circuit setting such asa lamp current setting.

FIG. 8 depicts yet another typical cross correlation sequence 804 from across correlator.

In certain cases, more than one distances may be detected in the form ofthe correlation sequence producing more than one spikes 811. This may betaken to mean that a single lamp illuminates more than one objects. Inthis case, an algorithm chooses the illumination to be effected. If thesignal from the peak with lesser delay is larger than a certainthreshold value (indicating the nearer of the bodies is larger than acertain size or optical presence (visual area times albedo)), it will bechosen as the primary illumination target. If the nearer body is small,the far body will be chosen as the primary illumination target.

In another embodiment, a weighted average of the delay of the peaks istaken to be an indicative delay and the illumination parameter is chosenbased on this indicative delay. The weights for the weighted average maybe heights of the corresponding peaks or a function of the heights ofthe corresponding peaks; the weight corresponding to a peak may be theheight of the peak divided by a number that is a fixed pre-determinedfunction of the delay of the particular peak.

In an embodiment, the above weighted average is taken without peakdetection, i.e. each delay value of the correlation sequence is used tocalculate the indicative delay. The delay values are weighted based onthe correlation sequence heights (amounts detected) in a manner similarto that of the preceding paragraph.

FIG. 9 depicts a situation 999 wherein a system 900 of producing evenillumination provided on a helmet 901 is illuminating a room 920.

Various lamps 902 illuminate all points in the room 920 directly (asillustrated by light path 915) as well as indirectly (as illustrated bylight path 916). By calculating the correlation sequences for eachlamp-detector pair and knowing the cones of illumination and location ofeach lamp and the one or more detectors, an approximate reconstructionof surrounding shapes is created. Reflections that are secondary (asillustrated by light path 917), tertiary and so forth help to furtherrefine this reconstruction.

In such a reconstruction, still objects may be detected separately frommoving objects. An accelerometer may be mounted on the helmet 901 or theillumination platform to help separate still and moving objects. Movingobjects may be flagged for many purposes. For rescue workers, etc., amoving object may mean an individual to be rescued or a coworker. Insecurity situations, moving objects may present a threat. An audiblealarm may be used to alert the user. Alternately, if the presence ofhumans is detected, the light in that direction may be dimmed so as tonot hurt the eyes of that human. For this purpose, humans may bedetected directly as well, e.g. through one or more video cameras.

The surrounding geometry may be detected by means other than (or inaddition to) flashing lamps as well, such as by multiple video cameras,depth sensing techniques, structured light projection, LIDAR, RADAR,SONAR, etc. This geometry may then be used to dim or brighten each lampso that an even illumination is achieved.

The one or more light detectors may have multiple pixels, and may have alens. Each pixel has a correlation being calculated for each lamp.Alternatively, there are multiple detectors with each detector having anarrow field of view. This creates a more detailed understanding of thesurrounding geometry, improving the accuracy of illumination and othergoals such as not blinding other humans and co-workers.

For each light detector, it is possible to detect the relative fractionof illumination received by that light detector that comes from eachparticular lamp. If multiple objects are being tracked, then objectsdetected at the same delay (or very close delays) bouncing light createdby lamps having overlapping regions of illumination may be detected asone object (especially if they are tracked to be moving in tandem), andfurthermore the relative fraction of illumination received by thatobject from each of its illuminating lamps is detected. Detection ofrelative fractions is done by comparing the heights of the peaks of thecorrelation sequences. The best illumination is achieved by setting theindividual lamp illumination levels such that various objects detectedwill have a level of illumination dependent on the detected distance ofthe objects, the illumination on the object being calculated based onthe illumination levels of the lamps illuminating it and the detectedrelative fractions.

FIG. 10 depicts an on-off flashing sequence.

The on-off flashing sequence drives a lamp to turn alternately on andoff. The on-off flashing sequence may have a different frequency fordifferent lamps. The on-off flashing sequence may have a duty cycle of50% or a variable duty cycle. The illumination output of the lamp may bechanged by changing the duty cycle. The illumination output of the lampmay be changed by changing the current passing through the lamp in the‘on’ phase.

In figures depicting flashing sequences, the x-axis represents time, andthe y-axis represents the flashing sequence value. According to variousembodiments of the present equation, the flashing sequence value may beinterpreted as the current through the lamp, some parameter affectingthe current through the lamp, the power output of the lamp, or theoptical output of the lamp. In the specific case of FIG. 10, theflashing sequence values may be thought of as a binary scheme where ‘0’implies the lamp is turned off and ‘1’ implies the lamp is turned on.

FIG. 11 depicts a sinusoidal flashing sequence.

The sinusoidal flashing sequence may have a different frequency fordifferent lamps. The illumination output of the lamp may be changed bychanging the peak current passing through the lamp.

In an embodiment, the sequence passed to the cross correlator is asquare of the sequence passed to the lamp. This is useful because thesequence passed to the lamp will create a particular lamp current andthe light power produced by the lamp will be approximately proportionalto the square of the current, and the light power detected at thedetector will be proportional to the light power produced by the lamp.For example, the sequence passed to the lamp may have positive andnegative peaks, whereas that passed to the correlator may be the oneshown in FIG. 11.

FIG. 12 depicts a sinusoidal flashing sequence with modulation depthless than 100%.

Modulation depth less than 100% implies the lamp does not turncompletely off while flashing. In this way, the perception of flashing(for human eyes or for video cameras) may be further reduced.Furthermore, more average illumination can be produced by a modulationdepth of less than 100% than that which can be produced by a modulationdepth of 100%. The illumination output of the lamp can be changed bychanging the modulation depth or changing the quiescent level of currentthrough the lamp.

FIG. 13 depicts a square wave flashing sequence with modulation depthless than 100%. The illumination output of the lamp can be changed bychanging the duty cycle, the modulation depth or the quiescent level ofcurrent through the lamp.

FIG. 14 depicts a random on-off flashing sequence.

The random sequence may be generated by a source of random bits, or apseudo-random calculation. A ‘1’ bit drives the corresponding lamp to beon and a ‘0’ bit drives it to be off.

The random sequence may be chosen such that on an average, a particularfraction of the randomly generated bits are ‘0’s and the others are ‘1’.In this way, the illumination output of the corresponding lamp may beset.

FIG. 15 depicts a random square wave flashing sequence with modulationdepth less than 100%. The illumination output of the lamp may be changedby changing the quiescent current level, the modulation depth or thefraction of bits that are ‘0’s.

FIG. 16 depicts a flashing sequence with more than two levels andmodulation depth less than 100%. A repeating or random sequence havingmore than two numerical levels may be used.

FIG. 17 depicts a law of calculating the illumination of a lamp based onthe detected distance. The illumination of the lamp is calculated to beproportional to the square of the detected distance. The calculatedillumination of the lamp will be used to set the actual illuminationoutput of the lamp using any of the techniques described in this patent,or standard techniques known in the art.

FIG. 18 depicts another law of calculating the illumination of a lampbased on the detected distance. At an intermediate range of detecteddistances, the illumination is calculated to be proportional to thesquare of the detected distance. In an embodiment, at a distance smallerthan the intermediate range of distances, the illumination is of ahigher value than that calculated by the square law, in this way,extremely dark zones in illumination will not be created. In anembodiment, at a distance larger than the intermediate range ofdistances, illumination falls off from the square law to a constant—inthis way large distances can be accommodated without exceeding lightingcircuit specifications.

FIG. 19 depicts yet another law of calculating the illumination of alamp based on the detected distance. The illumination of the lamp iscalculated proportional to the square of the detected distance plus aconstant: this constant reduces the sensitivity of the system todetected changes in the environment. In an embodiment, at a level beyondwhich the lighting circuit can manage, the illumination of the lamp iscalculated to be a fixed constant equal to the maximum permissibleillumination value for the lighting circuit.

FIG. 20 depicts a system of producing even illumination provided on ahand-held rod 2001. A hand held rod 2001 has lamps 2002 and lightdetectors 2003. The lamps 2002 and detector 2003 are absent from a gripportion of the rod 2001. This rod may be used to illuminate surroundingsin the dark, and creates even illumination on the surroundings using thefeatures of the present invention.

FIG. 21 depicts a system of producing even illumination provided on ahand-held illuminator 2101. A hand held illuminator 2101 has lamps 2102,light detectors 2103 and an on-off switch 2114. It may be held by aperson like a flashlight (battery torch), and creates even illuminationon the surroundings using the features of the present invention. Thelamps 2102 are provided towards one end of the illuminator 2101.

FIG. 22 depicts a system of producing even illumination provided on avehicle 2201. The vehicle 2201 has many lamps 2202 and some lightdetectors 2203. It will create even illumination on the surroundingsusing the features of the present invention.

FIG. 23 depicts a system of producing even illumination provided on arig 2301. A rig 2301 has lamps 2302 and light detectors 2303. It willcreate even illumination on the surroundings using the features of thepresent invention. Many more ways of assembling the system of thepresent invention may be imagined by a person having ordinary skill inthe art, and are within the scope of the present invention. The systemof the present invention may have a single lamp, and may change itsillumination level based on a detected distance.

An adaptive lighting system for even illumination is disclosed. It isunderstood that the embodiments described herein are for the purpose ofelucidation and should not be considered limiting the subject matter ofthe present patent. Various modifications, uses, substitutions,re-combinations, improvements, methods of productions without departingfrom the scope or spirit of the present invention would be evident to aperson skilled in the art.

I claim:
 1. A method comprising: providing a first rigid body, providinga plurality of lamps attached to the first rigid body, providing one ormore light detectors attached to the first rigid body, modulating thelight output of each lamp in accordance with a flashing sequence,detecting light reflected from the surroundings using the lightdetectors, correlating the output of a light detector with the flashingsequence to generate at least one delay estimate, and setting theillumination output of a lamp based on the delay estimate, wherein thestep of correlating the output of a light detector with a flashingsequence to generate at least one delay estimate comprises producing across correlation sequence from the flashing sequence and the output ofthe light detector.
 2. The method of claim 1 wherein producing the crosscorrelation sequence from the flashing sequence and the output of thelight detector comprises producing a present value of the k'th elementof the cross correlation sequence by multiplying the current value ofthe output of the light detector with the k'th previous value of theflashing sequence and adding this to an estimate derived from theprevious value of the k'th element of the cross correlation sequence. 3.The method of claim 2 wherein the estimate derived from the previousvalue of the k'th element of the cross correlation sequence iscalculated as the previous value of the k'th element of the crosscorrelation sequence multiplied by a constant.
 4. The method of claim 1wherein the step of correlating the output of a light detector with theflashing sequence to generate at least one delay estimate furthercomprises detecting a peak in a cross correlation sequence, andcalculating the delay estimate as the index of the peak in the crosscorrelation sequence
 5. The method of claim 1 wherein setting theillumination output of a lamp based on the delay estimate comprisessetting an illumination value that is higher for progressively higherdelay estimates
 6. A system comprising: a first body, a plurality oflamps attached to the first body, one or more light detectors attachedto the first body, and a cross correlator, wherein each lamp modulatesits light output in accordance with a flashing sequence, the lightdetectors detect light reflected from the surroundings, the crosscorrelator is configured to calculate a cross correlation sequence fromthe flashing sequence and the light detected by the light detector, andthe system is configured to change the illumination levels of theplurality of lamps based on the output of the cross correlator.
 7. Thesystem of claim 6 wherein the cross correlator uses the crosscorrelation sequence to produce a delay measurement
 8. The system ofclaim 6 wherein the cross correlator comprises one or more delayregisters arranged in a sequence such that the output of a delayregister is the input of the next delay register, and the input of thefirst delay register is the flashing sequence.
 9. The system of claim 8wherein the cross correlator further comprises one or more multipliers,each multiplier multiplying the output of a delay register with thevalue of the light detected by the light detector.
 10. The system ofclaim 9 wherein the cross correlator further comprises one or moreadders, each adder adding the value produced by a multiplier with theprevious output of the adder multiplied by a constant, to produce thecross correlation sequence.
 11. The system of claim 10 wherein the crosscorrelator further comprises a peak detector that detects at least onepeak in the cross correlation sequence, and each lamp in the pluralityof lamps changes its illumination level based on the index of the peakcalculated with respect to at least one cross correlation sequencecorresponding to that lamp.